public class ReplaceCheck
{
   /**
      A method to replace letters as follows:
      the letter e becomes 3, the letter i becomes 1,
      the letter l becomes 7, and the letter o becomes 0.
      @param str a string
      @return the string with the characters replaced
   */
   public static String replace(String str)
   {
      str = str.replace('e','3');
      str = str.replace('i','1');
      str = str.replace('l','7');
      str = str.replace('o','0');
      return str;
   }
}